Currently, a common authentication system generally includes a receive terminal and a transmit terminal, where rights are set for the transmit terminal, and the receive terminal receives authentication information transmitted by the transmit terminal, authenticates the transmit terminal, and after the authentication is passed, may allow the transmit terminal to perform an operation on the receive terminal. For example, in an access control system, all related technical solutions use a contactless proximity card such as an RFID (radio frequency) card or an IC card to perform a security authentication. The access control system using a proximity card for working is a proximity card access control system. The proximity card access control system transfers information to a card reader by using a proximity card. The card reader then transfers the proximity card information to an access controller. The access controller determines whether the card is a valid card, and transmits a determining result to the card reader. If the card is a valid card, the card reader gives out a “beep”, which represents that the card is a valid card, and meanwhile, the access controller unlocks an electric lock to open a door. When the card is an invalid card, the card reader does not perform any action and does not give out any sound, and the electric lock does not make any response. However, with continuous development of cracking technologies, currently, all RFID cards can be easily cracked, card information is replicated, and therefore a severe security problem exists. It is more difficult to crack an IC card. However, a method capable of cracking is also available currently, and the security problem still exists.
In addition to the foregoing proximity card access control system, some systems that transmit signals by using visible light begin to be applied. An access control system of this type mainly performs wireless information transmission by means of visible light. The system performs communication by flashing an LED light source at a high frequency, and generally includes a transmitter and a receiver. At the transmitter, an LED emits light and flashes at a frequency invisible to a human's eye, where in a specific period of time, presence of light indicates a binary signal “1”, and absence of light indicates a binary signal “0”. At the receiver (equivalent to a card reader), the light signal is converted into an electrical signal by using a photoelectric conversion component such as a photoresistor, and decoding is performed to obtain a corresponding card signal. Then the card signal is transferred to an access controller, and the access controller determines whether the transmitter has a right to open a door, and thereby determines whether to unlock the door. The foregoing solution in which visible light is used to perform short-range communication to transmit information of a transmitter is also feasible. However, because visible light can be emitted by only the triggered transmitter, and the light signal is transmitted by fast flashing, the light signal may be photographed by a high-speed camera, and visible light flashing information is obtained, and then transmitted information content is obtained by analyzing changes of flashing. Even if the information content is encrypted by the transmitter, the photographed content may also be illegally replicated, and a same transmit apparatus is made for transmitting the replicated light signal, and thereby the door of the photonic access control system can also be unlocked. Therefore, a security risk also exists.